Title: Plant Growth Regulators(Gibberellins)
1Plant Growth Regulators(Gibberellins)
- Prof. Dr./ Galal Ismail Eliwa
- Head Of Pomology Department
Faculty Of Agriculture Damietta University
E. mail/ geliwa2002_at_du.edu.eg
2Gibberellins
- Gibberellins are plant hormones that promote
growth, seed germination and leaf expansion. - They occur at low concentrations in vegetative
tissues but at higher concentration in
germinating seeds. - Induce cell elongation and cell division.
- Important for plant growth and development
through flowering and/ or seed germination.
3Gibberellins
- Discovered by Kurosawa, a Japanese Plant
Pathologist in 1928. - Rice plants infected by the fungus Gibberella
fujikuroi showed excessive stem elongation. - Symptom is called Bakane diseases foolish
seedling . - Chemical was extracted purified and names as
Gibberellic Acid (GA) - Now 84 different Gibberellins are available GA1
to GA84. - The most commonly occurring gibberllinis is GA3
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5Gibberellins
6Gibberellins
7Gibberellins
- Site
- Are produced in the shoot apex primarily in the
leaf primordial (young leaves), roots, and
developing seeds (developing endosperm) and
fruits. - Transport
- Made in the tissue in which it is used.
- Transport occurs through Xylem, Phloem, or cell
to cell. - Phloem seems to be most important route.
- Transport is not polar, as it is for Auxin.
8Gibberellins Actions
- Promotes stem elongation
- Stimulates cell division, cell elongation (or
both) and controls enzyme secretions. EX dwarf
cultivars can be treated with GA and grow to
normal heights indicates dwarf species lack
normal levels of GA. - dwarf short.,
- wild type tall
- dwarf GA tall
- Thus, Ga application
- stimulates elongation and
- acts on intact plants.
9Gibberellins Actions
1- Promotes stem elongation
10Gibberellins Actions in Tissue culture
11Gibberellins Actions in Tissue culture
12Gibberellins Actions
- 2- Overcomes dormancy in seeds
- Gibberellins also have a fundamental role in
breaking seed dormancy and stimulating
germination. - The endosperm of many seeds contains protein and
carbohydrate reserves upon which a developing
embryo relies for energy and nutrition. - These reserves must be mobilized and transported
to the embryo. - A range of hydrolytic and proteolysis enzymes
break down endosperm starches and proteins into
smaller, more easily transported molecules, such
as sugars and amino acids.
13Gibberellins Actions
- Overcomes dormancy in seeds
14Gibberellins Actions improve germination ???????
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15Gibberellins Actions improving seeds germination
16Gibberellins Actions
- Involved in parthenocarpic fruit development
17Gibberellins Actions
GA can induce fruit enlargment
- Gibberellins stimulate the stalk length of
seedless grapes to grow longer, thereby
alleviating compaction and it promotes elongation
of the fruit.
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22- Gibberellins Actions improving pome fruit set
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23Gibberellins Actions
- Promotes cell division elongation
Red Delicious apples untreated (Left) and treated
with a combination of benzyladenine, a cytokinin,
and GA4 GA3 (Right). Note The elongated almost
pointed shape.
24Gibberellins Actions improving pome fruit set
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40 ?????. - (1 ??? / 100 ??? ??? ???????? ?? ???? ?????
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30Gibberellins Actions
- Flowering
- GA stimulates bolting in Long Day plants and can
substitute for long days or cold treatments that
are necessary for flowering.
31Gibberellins Actions
- Sex expression
- In plants with separate male and female flowers,
GA application can determine sex. - For example, in cucumber and spinach, GA
treatment increases the proportion of male
flowers for seed production. - In maize, GA treatment causes female flower
development.
32Gibberellins Actions
- High sugar yield
- Growing of sugarcane enhances the growth of
internodes and increase the crop productivity
sugar yield of crop.
33Effect of pre-sowing seed treatment with
bio-regulators (GA3)
34Effect of Gibberellins on fruit set and
development
35Thank you for your attention